Electrolytic polarity when used in series with signal

[decc]

Just a quick question: How should the polarity of an electrolytic cap be arranged when using it in series with the audio signal? I would guess positive goes on the source side, but how do things work if you have a more complicated arrangement such as feedback networks or mixing multiple signals together?

Thanks

[R.G.]

The audio signal does not matter. What matters is the DC polarity. Electrolytics MUST be used with the proper DC polarity.

If there is a signal going through them, two things must be correct:
(a) there must be a DC bias across them in the correct direction
(b) the signal must be small enough that the side swinging opposite to the DC bias mus never make the instantaneous voltage be reversed.

It is true that very small signals may not cause immediate problems with an electro cap. However, each reverse polarity of any magnitude speeds up aging of the insulator. Then it's a horse race between normal aging, signal induced again, and re-growth of the insulator by DC bias. It's bad practice.

[decc]

That's how I understood it, but there were a few schematics I've seen where it appears you will have reverse bias due to the audio signal during normal operation. I thought maybe it didn't matter if there were only reverse transients over a certain frequency.

I'll just stick to non-polars in my designs (outside of power filtering) and avoid the situation all together.